1. Field of the Invention
The present invention relates to a snap ring support device for an automatic transmission, and, in particular, to a recessed groove structure for a snap ring supporting a return spring for a hydraulic actuator.
2. Description of the Prior Art
Conventionally, an automatic transmission, as shown in FIG. 5(a) and (b), uses a hydraulic actuator 102 comprising a pair of cylinders 100a, 100b and a piston 101 to operate the clutch and brakes. The actuator 102 has a return spring 103 which is positioned on the rear surface of the piston 101. A receiving member 105 for retaining the return spring is held and prevented from being removed by means of a snap ring 107 mounted in an annular recessed groove 106 formed in each of the cylinders 100a, 100b. The reaction force of the return spring 103 is borne by the recessed groove 106 through the receiving member 105 and the snap ring 107.
In automatic transmissions, the development of higher horsepower vehicles and FF (front engine/front drive) vehicles, and the like has necessitated higher volume, more compactness (especially axial shortening), and more weight reduction, leading to a reduction in cost.
As shown in FIG. 5(a), reduction of weight can be provided by fabricating the cylinder 100a from a light weight material such as aluminum and the like, but use of a light weight material leads to a reduction in strength, making it necessary to position the recessed groove 106 at a prescribed distance from the end surface, so that the groove 106 receives the reaction force of the spring exerted on the snap ring 107 through the receiving member 105. This is one reason why a shortening of the axial dimension is hindered.
In addition, as shown in FIG. 5(b), when the cylinder 100b is formed from a high strength material such as steel or cast iron, it is possible to set the recessed groove 106 close to the end surface of the cylinder, but, the high strength material leads to a high specific gravity, and is a detergent to weight reduction.